1 | import videojs from 'video.js';
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2 | import { createTransferableMessage } from './bin-utils';
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3 |
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4 | export const REQUEST_ERRORS = {
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5 | FAILURE: 2,
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6 | TIMEOUT: -101,
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7 | ABORTED: -102
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8 | };
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9 |
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10 | /**
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11 | * Turns segment byterange into a string suitable for use in
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12 | * HTTP Range requests
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13 | *
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14 | * @param {Object} byterange - an object with two values defining the start and end
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15 | * of a byte-range
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16 | */
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17 | const byterangeStr = function(byterange) {
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18 | let byterangeStart;
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19 | let byterangeEnd;
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20 |
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21 | // `byterangeEnd` is one less than `offset + length` because the HTTP range
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22 | // header uses inclusive ranges
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23 | byterangeEnd = byterange.offset + byterange.length - 1;
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24 | byterangeStart = byterange.offset;
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25 | return 'bytes=' + byterangeStart + '-' + byterangeEnd;
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26 | };
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27 |
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28 | /**
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29 | * Defines headers for use in the xhr request for a particular segment.
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30 | *
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31 | * @param {Object} segment - a simplified copy of the segmentInfo object
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32 | * from SegmentLoader
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33 | */
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34 | const segmentXhrHeaders = function(segment) {
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35 | let headers = {};
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36 |
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37 | if (segment.byterange) {
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38 | headers.Range = byterangeStr(segment.byterange);
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39 | }
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40 | return headers;
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41 | };
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42 |
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43 | /**
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44 | * Abort all requests
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45 | *
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46 | * @param {Object} activeXhrs - an object that tracks all XHR requests
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47 | */
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48 | const abortAll = (activeXhrs) => {
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49 | activeXhrs.forEach((xhr) => {
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50 | xhr.abort();
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51 | });
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52 | };
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53 |
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54 | /**
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55 | * Gather important bandwidth stats once a request has completed
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56 | *
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57 | * @param {Object} request - the XHR request from which to gather stats
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58 | */
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59 | const getRequestStats = (request) => {
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60 | return {
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61 | bandwidth: request.bandwidth,
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62 | bytesReceived: request.bytesReceived || 0,
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63 | roundTripTime: request.roundTripTime || 0
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64 | };
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65 | };
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66 |
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67 | /**
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68 | * If possible gather bandwidth stats as a request is in
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69 | * progress
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70 | *
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71 | * @param {Event} progressEvent - an event object from an XHR's progress event
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72 | */
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73 | const getProgressStats = (progressEvent) => {
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74 | const request = progressEvent.target;
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75 | const roundTripTime = Date.now() - request.requestTime;
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76 | const stats = {
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77 | bandwidth: Infinity,
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78 | bytesReceived: 0,
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79 | roundTripTime: roundTripTime || 0
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80 | };
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81 |
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82 | stats.bytesReceived = progressEvent.loaded;
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83 | // This can result in Infinity if stats.roundTripTime is 0 but that is ok
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84 | // because we should only use bandwidth stats on progress to determine when
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85 | // abort a request early due to insufficient bandwidth
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86 | stats.bandwidth = Math.floor((stats.bytesReceived / stats.roundTripTime) * 8 * 1000);
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87 |
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88 | return stats;
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89 | };
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90 |
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91 | /**
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92 | * Handle all error conditions in one place and return an object
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93 | * with all the information
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94 | *
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95 | * @param {Error|null} error - if non-null signals an error occured with the XHR
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96 | * @param {Object} request - the XHR request that possibly generated the error
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97 | */
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98 | const handleErrors = (error, request) => {
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99 | if (request.timedout) {
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100 | return {
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101 | status: request.status,
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102 | message: 'HLS request timed-out at URL: ' + request.uri,
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103 | code: REQUEST_ERRORS.TIMEOUT,
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104 | xhr: request
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105 | };
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106 | }
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107 |
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108 | if (request.aborted) {
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109 | return {
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110 | status: request.status,
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111 | message: 'HLS request aborted at URL: ' + request.uri,
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112 | code: REQUEST_ERRORS.ABORTED,
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113 | xhr: request
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114 | };
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115 | }
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116 |
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117 | if (error) {
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118 | return {
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119 | status: request.status,
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120 | message: 'HLS request errored at URL: ' + request.uri,
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121 | code: REQUEST_ERRORS.FAILURE,
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122 | xhr: request
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123 | };
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124 | }
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125 |
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126 | return null;
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127 | };
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128 |
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129 | /**
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130 | * Handle responses for key data and convert the key data to the correct format
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131 | * for the decryption step later
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132 | *
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133 | * @param {Object} segment - a simplified copy of the segmentInfo object
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134 | * from SegmentLoader
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135 | * @param {Function} finishProcessingFn - a callback to execute to continue processing
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136 | * this request
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137 | */
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138 | const handleKeyResponse = (segment, finishProcessingFn) => (error, request) => {
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139 | const response = request.response;
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140 | const errorObj = handleErrors(error, request);
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141 |
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142 | if (errorObj) {
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143 | return finishProcessingFn(errorObj, segment);
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144 | }
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145 |
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146 | if (response.byteLength !== 16) {
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147 | return finishProcessingFn({
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148 | status: request.status,
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149 | message: 'Invalid HLS key at URL: ' + request.uri,
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150 | code: REQUEST_ERRORS.FAILURE,
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151 | xhr: request
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152 | }, segment);
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153 | }
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154 |
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155 | const view = new DataView(response);
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156 |
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157 | segment.key.bytes = new Uint32Array([
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158 | view.getUint32(0),
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159 | view.getUint32(4),
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160 | view.getUint32(8),
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161 | view.getUint32(12)
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162 | ]);
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163 | return finishProcessingFn(null, segment);
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164 | };
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165 |
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166 | /**
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167 | * Handle init-segment responses
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168 | *
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169 | * @param {Object} segment - a simplified copy of the segmentInfo object
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170 | * from SegmentLoader
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171 | * @param {Function} finishProcessingFn - a callback to execute to continue processing
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172 | * this request
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173 | */
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174 | const handleInitSegmentResponse = (segment, finishProcessingFn) => (error, request) => {
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175 | const response = request.response;
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176 | const errorObj = handleErrors(error, request);
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177 |
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178 | if (errorObj) {
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179 | return finishProcessingFn(errorObj, segment);
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180 | }
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181 |
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182 | // stop processing if received empty content
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183 | if (response.byteLength === 0) {
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184 | return finishProcessingFn({
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185 | status: request.status,
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186 | message: 'Empty HLS segment content at URL: ' + request.uri,
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187 | code: REQUEST_ERRORS.FAILURE,
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188 | xhr: request
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189 | }, segment);
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190 | }
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191 |
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192 | segment.map.bytes = new Uint8Array(request.response);
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193 | return finishProcessingFn(null, segment);
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194 | };
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195 |
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196 | /**
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197 | * Response handler for segment-requests being sure to set the correct
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198 | * property depending on whether the segment is encryped or not
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199 | * Also records and keeps track of stats that are used for ABR purposes
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200 | *
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201 | * @param {Object} segment - a simplified copy of the segmentInfo object
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202 | * from SegmentLoader
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203 | * @param {Function} finishProcessingFn - a callback to execute to continue processing
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204 | * this request
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205 | */
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206 | const handleSegmentResponse = (segment, finishProcessingFn) => (error, request) => {
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207 | const response = request.response;
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208 | const errorObj = handleErrors(error, request);
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209 |
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210 | if (errorObj) {
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211 | return finishProcessingFn(errorObj, segment);
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212 | }
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213 |
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214 | // stop processing if received empty content
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215 | if (response.byteLength === 0) {
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216 | return finishProcessingFn({
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217 | status: request.status,
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218 | message: 'Empty HLS segment content at URL: ' + request.uri,
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219 | code: REQUEST_ERRORS.FAILURE,
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220 | xhr: request
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221 | }, segment);
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222 | }
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223 |
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224 | segment.stats = getRequestStats(request);
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225 |
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226 | if (segment.key) {
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227 | segment.encryptedBytes = new Uint8Array(request.response);
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228 | } else {
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229 | segment.bytes = new Uint8Array(request.response);
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230 | }
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231 |
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232 | return finishProcessingFn(null, segment);
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233 | };
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234 |
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235 | /**
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236 | * Decrypt the segment via the decryption web worker
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237 | *
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238 | * @param {WebWorker} decrypter - a WebWorker interface to AES-128 decryption routines
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239 | * @param {Object} segment - a simplified copy of the segmentInfo object
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240 | * from SegmentLoader
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241 | * @param {Function} doneFn - a callback that is executed after decryption has completed
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242 | */
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243 | const decryptSegment = (decrypter, segment, doneFn) => {
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244 | const decryptionHandler = (event) => {
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245 | if (event.data.source === segment.requestId) {
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246 | decrypter.removeEventListener('message', decryptionHandler);
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247 | const decrypted = event.data.decrypted;
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248 |
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249 | segment.bytes = new Uint8Array(decrypted.bytes,
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250 | decrypted.byteOffset,
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251 | decrypted.byteLength);
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252 | return doneFn(null, segment);
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253 | }
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254 | };
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255 |
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256 | decrypter.addEventListener('message', decryptionHandler);
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257 |
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258 | // this is an encrypted segment
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259 | // incrementally decrypt the segment
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260 | decrypter.postMessage(createTransferableMessage({
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261 | source: segment.requestId,
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262 | encrypted: segment.encryptedBytes,
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263 | key: segment.key.bytes,
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264 | iv: segment.key.iv
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265 | }), [
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266 | segment.encryptedBytes.buffer,
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267 | segment.key.bytes.buffer
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268 | ]);
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269 | };
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270 |
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271 | /**
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272 | * The purpose of this function is to get the most pertinent error from the
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273 | * array of errors.
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274 | * For instance if a timeout and two aborts occur, then the aborts were
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275 | * likely triggered by the timeout so return that error object.
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276 | */
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277 | const getMostImportantError = (errors) => {
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278 | return errors.reduce((prev, err) => {
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279 | return err.code > prev.code ? err : prev;
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280 | });
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281 | };
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282 |
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283 | /**
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284 | * This function waits for all XHRs to finish (with either success or failure)
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285 | * before continueing processing via it's callback. The function gathers errors
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286 | * from each request into a single errors array so that the error status for
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287 | * each request can be examined later.
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288 | *
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289 | * @param {Object} activeXhrs - an object that tracks all XHR requests
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290 | * @param {WebWorker} decrypter - a WebWorker interface to AES-128 decryption routines
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291 | * @param {Function} doneFn - a callback that is executed after all resources have been
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292 | * downloaded and any decryption completed
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293 | */
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294 | const waitForCompletion = (activeXhrs, decrypter, doneFn) => {
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295 | let errors = [];
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296 | let count = 0;
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297 |
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298 | return (error, segment) => {
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299 | if (error) {
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300 | // If there are errors, we have to abort any outstanding requests
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301 | abortAll(activeXhrs);
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302 | errors.push(error);
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303 | }
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304 | count += 1;
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305 |
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306 | if (count === activeXhrs.length) {
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307 | // Keep track of when *all* of the requests have completed
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308 | segment.endOfAllRequests = Date.now();
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309 |
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310 | if (errors.length > 0) {
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311 | const worstError = getMostImportantError(errors);
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312 |
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313 | return doneFn(worstError, segment);
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314 | }
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315 | if (segment.encryptedBytes) {
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316 | return decryptSegment(decrypter, segment, doneFn);
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317 | }
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318 | // Otherwise, everything is ready just continue
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319 | return doneFn(null, segment);
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320 | }
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321 | };
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322 | };
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323 |
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324 | /**
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325 | * Simple progress event callback handler that gathers some stats before
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326 | * executing a provided callback with the `segment` object
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327 | *
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328 | * @param {Object} segment - a simplified copy of the segmentInfo object
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329 | * from SegmentLoader
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330 | * @param {Function} progressFn - a callback that is executed each time a progress event
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331 | * is received
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332 | * @param {Event} event - the progress event object from XMLHttpRequest
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333 | */
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334 | const handleProgress = (segment, progressFn) => (event) => {
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335 | segment.stats = videojs.mergeOptions(segment.stats, getProgressStats(event));
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336 |
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337 | // record the time that we receive the first byte of data
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338 | if (!segment.stats.firstBytesReceivedAt && segment.stats.bytesReceived) {
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339 | segment.stats.firstBytesReceivedAt = Date.now();
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340 | }
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341 |
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342 | return progressFn(event, segment);
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343 | };
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344 |
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345 | /**
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346 | * Load all resources and does any processing necessary for a media-segment
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347 | *
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348 | * Features:
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349 | * decrypts the media-segment if it has a key uri and an iv
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350 | * aborts *all* requests if *any* one request fails
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351 | *
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352 | * The segment object, at minimum, has the following format:
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353 | * {
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354 | * resolvedUri: String,
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355 | * [byterange]: {
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356 | * offset: Number,
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357 | * length: Number
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358 | * },
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359 | * [key]: {
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360 | * resolvedUri: String
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361 | * [byterange]: {
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362 | * offset: Number,
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363 | * length: Number
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364 | * },
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365 | * iv: {
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366 | * bytes: Uint32Array
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367 | * }
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368 | * },
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369 | * [map]: {
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370 | * resolvedUri: String,
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371 | * [byterange]: {
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372 | * offset: Number,
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373 | * length: Number
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374 | * },
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375 | * [bytes]: Uint8Array
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376 | * }
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377 | * }
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378 | * ...where [name] denotes optional properties
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379 | *
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380 | * @param {Function} xhr - an instance of the xhr wrapper in xhr.js
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381 | * @param {Object} xhrOptions - the base options to provide to all xhr requests
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382 | * @param {WebWorker} decryptionWorker - a WebWorker interface to AES-128
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383 | * decryption routines
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384 | * @param {Object} segment - a simplified copy of the segmentInfo object
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385 | * from SegmentLoader
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386 | * @param {Function} progressFn - a callback that receives progress events from the main
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387 | * segment's xhr request
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388 | * @param {Function} doneFn - a callback that is executed only once all requests have
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389 | * succeeded or failed
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390 | * @returns {Function} a function that, when invoked, immediately aborts all
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391 | * outstanding requests
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392 | */
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393 | export const mediaSegmentRequest = (xhr,
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394 | xhrOptions,
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395 | decryptionWorker,
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396 | segment,
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397 | progressFn,
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398 | doneFn) => {
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399 | const activeXhrs = [];
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400 | const finishProcessingFn = waitForCompletion(activeXhrs, decryptionWorker, doneFn);
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401 |
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402 | // optionally, request the decryption key
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403 | if (segment.key) {
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404 | const keyRequestOptions = videojs.mergeOptions(xhrOptions, {
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405 | uri: segment.key.resolvedUri,
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406 | responseType: 'arraybuffer'
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407 | });
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408 | const keyRequestCallback = handleKeyResponse(segment, finishProcessingFn);
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409 | const keyXhr = xhr(keyRequestOptions, keyRequestCallback);
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410 |
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411 | activeXhrs.push(keyXhr);
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412 | }
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413 |
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414 | // optionally, request the associated media init segment
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415 | if (segment.map &&
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416 | !segment.map.bytes) {
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417 | const initSegmentOptions = videojs.mergeOptions(xhrOptions, {
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418 | uri: segment.map.resolvedUri,
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419 | responseType: 'arraybuffer',
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420 | headers: segmentXhrHeaders(segment.map)
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421 | });
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422 | const initSegmentRequestCallback = handleInitSegmentResponse(segment,
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423 | finishProcessingFn);
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424 | const initSegmentXhr = xhr(initSegmentOptions, initSegmentRequestCallback);
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425 |
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426 | activeXhrs.push(initSegmentXhr);
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427 | }
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428 |
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429 | const segmentRequestOptions = videojs.mergeOptions(xhrOptions, {
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430 | uri: segment.resolvedUri,
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431 | responseType: 'arraybuffer',
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432 | headers: segmentXhrHeaders(segment)
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433 | });
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434 | const segmentRequestCallback = handleSegmentResponse(segment, finishProcessingFn);
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435 | const segmentXhr = xhr(segmentRequestOptions, segmentRequestCallback);
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436 |
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437 | segmentXhr.addEventListener('progress', handleProgress(segment, progressFn));
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438 | activeXhrs.push(segmentXhr);
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439 |
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440 | return () => abortAll(activeXhrs);
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441 | };
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